An inductor formed by planar processing includes a magnetic core layer of a laminate of alternating layers of magnetic material and dielectric, to reduce eddy current losses. The magnetic material includes at least 80 percent cobalt, at least 1 percent tantalum and at least 1 percent zirconium. Patterning the magnetic laminate layer has been problematic. Wet etch processes leave residue and degrade exposed copper interconnects. Dry etch processes such as ion milling have high manufacturing costs.